Why it's hard to mock Barack Obama

I got this from Andrew Sullivan:

"[Obama is] just one of those guys, you know, like Will Smith. There's no Will Smith jokes. There's no Brad Pitt jokes. You know, what are you going to say? "Ooh, you used to have sex with Jennifer Anniston. Now you have sex with Angelina Jolie. You're such a loser." What do you say? "Ooh, your movies are big. You make $20 million." There's nothing to say about Brad Pitt...[With Obama it's] like "Ooh, you're young and virile and you've got a beautiful wife and kids. You're the first African-American president." You know, what do you say?," - Chris Rock.